BIND and UDP tuning

Browne, Stuart Stuart.Browne at team.neustar
Mon Oct 1 00:45:09 UTC 2018


> -----Original Message-----
> From: bind-users On Behalf Of Alex

<snip> 

> I'm leaning towards that, too. The problem persists even when using
> the provider's DNS servers. I thought for sure I'd see some verifiable
> info from other people having problems with cable, such as from
> dslreports, etc, but there really hasn't been anything. The comment
> made about DOCSIS earlier in this thread was helpful.
> 
> Do you believe it could be impacting all data, not just bind/DNS/UDP?
> 
> Do people not generally use cable as even a fallback link for
> secondary services? I figured it was because there's no SLA, not
> because it doesn't work well with many protocols. I'd imagine services
> like Netflix and youtube don't have problems is because they 1) don't
> require a lot of DNS traffic and 2) http is a really simple protocol
> and 3) the link is probably engineered to be used for that?

I use sendmail and bind at home for my purposes, and don't have these sorts of issues. But what probably solves this for most users is the fact that most home-sort-of-users use TCP rather than UDP.

UDP is designed as a lossy protocol; no resends, no guaranteed delivery at a protocol level. If you're really concerned with the occasional SERVFAIL due to this (which your stub resolver should be retrying), you could try convincing BIND to recurse using TCP only. It's not a good idea (and I'm pretty sure doesn't have the option to do it natively)...

Stuart


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